My husband is a retail manager of a small chain location. He had an incident with a couple customers in which the customer accused my husband on social media of cussing at their child which was backed up by the retail clerk on duty to be untrue. Now he is

My husband is a retail manager, one night a couple and their child come into the store. while the parents are shopping the child pulls of a rubber safety ring from a rack and starts swinging it around. My husband sees this and goes to the father and asks him to ask his child not to do this, he was interrupted by the mother yelling about my husband cussing at her child, my husband never spoke to the child. They left the store and complained on social media. He was sent home soon after and has been told that they will let him know after the investigation, he has been off work for 5 days while they investigate. The clerk on duty that night verified that my husband Chris never spoke to the child or spoke out of anger with the customer. He is now being demoted. Is this legal?